Art of producing valuable aromatic hydrocarbons from petroleum fractions



NOV. 21, 1944. R, ROSEN 2,363,263

ART 0F PRODUCING VALUABLE AROMATIC HYDROCARBONS FROM PETROLEUM FRACTIONS Filed June 30, 1938 'SEPA RA T//vc EXfgA c 770A/ To w52,

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' the present process. y

Patented'yNov. 21, 1944 ART 01? PRODUCING 'VALUABLE AROMATIC FROM PETROLEUM.

HYDROCABBONS FRACTIONS Raphael Rosen, Elizabeth, N. J., asslgnor to "Standard Oil Development Company, a corporation ol Delaware A Application June 30, 1938, SerialNo. 216,637

l1 claim. (ci.

not be passed through the extraction; the other Ifhe presentinvention relates to the art of producing valuable aromatic hydrocarbons from pef troleum fractions, especially useful for blending with naphthas to make. aviation and other type gasolines. `The process will be fully underst from the following description.

The drawing is a diagrammatic View in sectional elevation of an apparatus for carrying out L In the drawing numeral I designates a feed line through which `is supplied a naphtha or naphtha distillate of the type rich4 in naphthenic l hydrocarbons. Such fractions are obtained fro1n` crudes found in various parts of the world, for

example from certain Texas and California crudes, as well as those from Venezuela and other foreign countries. -The naphtha distillate, by

' which is meant a fraction of the crude contain- 'ing' the naphtha Oli asoline constituents, is

A passed into a, solvent extraction apparatus 2.

. This apparatus is conveniently in the form of acolumn fitted with contact devices such as packlng'orbubble plates 3. The pipe I discharges into one end of the tower and into the opposite vend a suitable solvent is discharged by pipe 4 so that the oil and solvent flow countercurrently to each other in the treating tower. If the solvent is heavier than the oil, then itl will be introduced at the top of the column, as shown in the drawing, but in some instances lower specic gravity solvents are used and in such cases the -flow will be reversed, the solvent added at the lower vpart of the column. From the following description itwill be assumed that the solvent is of greater specic gravityl and higher boiling range than the oil. i

'I'he extracted oil is withdrawn from the tower by pipe 5. This product is richer in aromatic fractions than is the feed, and the raiilnate taken oli by pipe 6 is largely saturated, containing both paramnic and ,fnaphthenic fractions. Both extract and railinate contain the solvent. The oil removed by pipe 8 is heated at 1 and discharged into a separating still 8, in which the oil is vamm a heating con 12.' if affeed stock which is very rich in naphthenes is available, it may be introduced directly into the coil I2 by a pipe Il and pump" I4, without previous extraction and it containing aromatics is preferably first extracted,

as shown.

The naphthene rich fractions are heated in the coil l2 to a dehydrogenating temperature and then passed through a catalytic dehydrogenating reactor I2', but the process s nay be non-jcatalytic, if preferred, and the coil may be made sulciently long so that the drum may be omitted.

lIn any case the dehydrogenated products are `-cooled at I and the liquidis separated from hydrogen-and other gases in separator I6. The gases are bled oil by a pipe Il and the dehydrogenated liquid is/now subjected to solvent extraction in order t separate the aromatic fractions produced by dehydrogenation from the aliphatic fractions. The apparatus for this extraction may be of any suitable form, but preferably consists of atower I8 similar to tower 3 described above.

'I'hesolvent is shown entering at the top of the tower by pipe I9 and the raiiinate, consisting mainly'of parafinic fractions; is taken o from the top of the tower by a pipe 20. 'I'his oil is separated from the solvent by distillation in the pipe heater 2l and tower still 22. 'I'he evaporated oil is condensed at 23 and is collected at 24. The extract is taken from the tower I8 by a pump 25 and is separated from the solventby distillation in the coil 26 and tower 2.1 and is 4 and I9 respectively as stated above.

will be understood that if two ,different feed stocks Y areavailable, both may be u sed inthe same apparatus. 'It one is richer in aromatics, it need In the present process the oil may be a naphtha of lnishedboiling range suitable for gasoline, boiling for instance from or 200 F. to 400 or 500" F. and may be taken from any one of the well known crudes which are rich in aromatic fractions. If thereis a substantial amount of aromatics in the original crude, then it is desirable `rst to remove these by solvent extraction as shown on the drawing previously described. The railinate from this extraction is rich in naphthenes and is dehydrogenated and.

then re-extracted so as to separate the aromatics produced by the dehydrogenation. The aromatic fraction so produced may then be combined as shown in the drawing previously described with the aromatic extract obtained from thev originalcr'ude. The extraction process may be'accomplished with any of a variety of different solvents suitable for this purpose. 'I'hese are well known in the art. 'I'hey include liquid sulfur dioxide or mixtures thereof with carbon dioxide,

With such a solvent, the extraction is preferably carried out at a temperature below -20 F., where the solvents are very selective. Other suitable solvents are aniline, nitrobenzol. cresol, phenol, beta beta dichlor ethyl ether, furfural, triethylene glycol and the like. The extraction conditions for these various solvents dier, but

the characteristics of each of the solvents are.

well known in the art at the present time and a detailed description of these conditions should not be required.

The dehydrogenation process is preferably catalytic and is conducted at low or moderate pres- 4 oxides such as alumina, zinc oxide, thoria, mag

nesia, and the like.

. While a catalytic process is preferred. it will be understood that dehydrogenation may be accomplished without the use of any catalyst. It

is preferred to obtain dehydrogenation without decomposition of the carbon structuresof the products or with at least a minimum ofsuch portions ci!y gaseous hydrocarbons. This-catalytic reforming is capable of increasing the aromatic content of naphthenic naphthas to a considerably higher degree and with much less formation of hydrocarbon gas than is possible with previous reforming. Y

To illustrate the nature of the present operation, the following example may be considered:

A naphtha boiling from 115 to 400 F. was ob `tained from Lagunillas crude and was dehydrogenated by passing through a reactor at a rate of .'79 volumes/volume of reactive space per hour,

while at a temperature of 1045 F. The catalyst was a mixture ofchromium oxide and zinc oxide. The boiling range of the product was substantially the same as of the feed, but a considerable volurne of gas of low specific gravity was formed, very rich in free hydrogen. The gravity of the feed oil was 54.6 API and that of the product 52.6. The aniline point of the feed was 121 F. and that of the product 94 F. The dehydrogenated product obtained as above was distilled so as to get a fraction having a boiling range of 200 to 300 F., and this material was extracted once with 1.2 volumes of aniline at 71 F. About 21.5% of the fraction was removed by the extraction and this fraction was found to have a gravity of 43.8 API. The product was very aromatic and when used in concentration in 20% gasoline had a blending value of '16.

The present invention is not to be limited to any theory of the mechanism of the process, nor to any particular solvent or dehydrogenation method, but only t0 the following claim in which it is desired to claim all novelty inherent in the invention.

I claim:

A process for producing a very aromatic prod- ,uct from petroleum which comprises separating naphtha boiling between about 100 to 500 F. from a crude petroleum rich in naphthenic compounds, dehydrogenating the naphtha by passing it through a reactor at a temperature of approximately 1045 F. over a catalyst whereby a product of substantially the boiling range ofthe naphtha is producedcontaining aromatic compounds in the presence of non-aromatic compounds, distllling the dehydrogenated product to form afraction honing between about 20o and 300 F.,

extracting the fraction with la solvent adapted to separate the aromatic from the non-aromatic fractions and removing the solvent whereby a very aromatic product is obtained.

l'\..APHAl.I.|I ROSEN. 

